1. Field of the Invention
The present invention generally relates to a protective, load dispersing device which prevents the slippage of a ladder as well as preventing damage to the surface against which the ladder rests. An in alternate embodiment, the protective bumpers can be used to protect one or more sides of a three dimensional object.
2. Description of the Background of the Invention
There are two common problems arising from the use of ladders in work on buildings, particularly on or near their roofs, that are minimized by the novel device according to this invention.
First, the thrust component of the combined weight of the ladder, the user, and any equipment the user may be carrying is commonly born by two small areas of contact between the side members of the ladder and the structure receiving the ladder. The tendency of that thrust component on the gutter is to dent it, and in the worst case to deform the strengthening formed edge of the gutter so that it collapses. As the gutter flexes it can readily be seen that the areas of contact between it and the side members of the ladder decrease from that of the flat contact between the underside of the ladder's side members and the gutter edge, until the gutter edge supports only the corners of the undersides of the ladder side members. It is then that the maximum deformation of the gutter profile and the greatest damage to its paint occur. Added to the causes of paint damage are the sliding which occurs between the gutter's paint coating and the side members of the ladder, as the ladder flexes while the user is moving on it.
Second, ladders have the tendency to slip sideways when there are small movements by their feet, typically caused by the feet being placed in error by the user on soft ground or on unstable propping material. Since the width of a ladder is small compared with its height, when the weight of a user of the ladder is near its top, the rate of sideways slippage accelerates the farther the line of the feet diverges from the horizontal. As will be seen, this problem has in previous inventions been dealt with by fixing in some way the upper part of the ladder to the building, its roof or its gutter. That purported solution is unsatisfactory, however, because fixing the top may require the ladder's feet to be in a location which may not be stable, and the user is then dependent for his security on the upper fixing means, obviously not as reliable as a stable location for the feet. The device according to the present invention overcomes that defect of the earlier inventions by allowing the upper part of the ladder freedom of positioning both along and transverse to the gutter or other building feature upon which the upper part of the ladder is to rest, thereby permitting the feet of the ladder to be located on the necessary firm and level support.
All these tendencies to damage are eliminated by use of the device according to this invention, which places a flexible, non-slip, non-abrasive, non-electrically-conductive bearing surface between the ladder's side members and the gutter or other feature of the structure against which the ladder rests.
This invention also has the important advantage that it may be manufactured in materials that enable it to provide electrical insulation from the upper support surface for the ladder on which it is mounted.
Several other patents have been granted for inventions intended to prevent ladders from slipping along their upper support surfaces, but none so far has offered a solution to the foregoing problems of damage to the upper support surface and slipping. For example, U.S. Pat. No. 3,948,353, issued to Lane, teaches an non-free-standing ladder with flanged and lined cut-out portions along the side members of its upper section, said cut-out portions being intended to hook over the upper support, with the lining providing an anti-skid surface. It can be readily seen that manufacturing the ladder claimed in Lane with its flanged cut-out portions would be more expensive than for the standard metal or Fiberglas ladder commonly available, and to which this invention is adapted, of which the side members are extruded or molded with the same cross section along their entire lengths. Furthermore, since the ladder in Lane is intended to be hooked over a fixed upper support, such as a gutter, the ladder user has a restricted opportunity of adjusting the foot of the ladder to find a stable lower support, which is a safety measure of even greater importance than any such measures taken at the upper end of the ladder, since, without a stable lower support, the ladder should not be used. Also, when the ladder is being used, that is, when weight is applied to it, any flexing of the ladder, which always occurs, and any effort of the lower end of the ladder to find a stable footing, will tend to drag down the upper support over which the ladder is hooked. This might seriously damage, for example, a lightweight aluminum gutter used as the upper support.
U.S. Pat. No. 5,121,813, issued to Funston, teaches a rigid leg member to provide stable support for the lower end of a ladder, combined with a hooking support for hooking to, for example, a gutter. A separate lower support as in Funston is not part of the present invention, which relies on the user establishing a stable footing for his ladder, and assists the user in doing this by allowing the upper support of the ladder to be adjusted up or down the length of this invention, without hooks or fixing means at the upper support. The tendency to drag the exemplary gutter down by hooked elements is the same in Funston as in Lane, that is when the ladder flexes in use. Also, the metal hook elements in Funston would tend to scratch the painted surface of the upper support.
U.S. Pat. Nos 4,924971, issued to Rice, 4,601,365, issued to Davis, and 4,580,661, issued to Thomson, Jr., all teach inventions that require for their operation installation on or in the upper support, which in the cases of Davis and Thomson, Jr. appear to be restricted to gutters. Obviously, such installation negates the purpose of the respective invention to a certain extent, since the ladder must be used initially to install the Rice, Davis and Thompson,Jr., inventions, and until such installation is done the respective inventions are ineffective. This contrasts with the benefits of the present invention, where the safety device to which the invention is directed is installed on the ladder before use and requires no fixing to the upper or lower ladder support surface. The present invention also enables a non-free-standing ladder on which it is used to be lengthened or shortened, and moved along the building, or other structure on which work is proceeding, without adjustment of the device. In the case of Rice, the invention must be reinstalled at the upper support for each new location in order for the ladder to be moved; in the cases of Davis and Thompson, Jr., the inventions must be moved when the ladder is moved, or additional devices according to the respective inventions must be installed at the new locations.
U.S. Pat. Nos. 5,293,958, issued to Swiderski et al., and 4,754,842, issued to Southern both teach devices for propping the tops of ladders away from walls. This feature enables a ladder user to work up to the level of the top of a wall or possibly slightly above, but does permit the user to step off the ladder on to the roof of a structure, to do which would require according to standard practical that the ladder extend over the lower edge of the roof by between one and three feet. By contrast, the present invention, of which one of the advantages is that it promotes the safety of stepping from a ladder to a roof allows the ladder to rest against lower edge of the roof, against a gutter, for example, while reducing the possibility of the ladder's slipping sideways, according to the standard recommendations.
U.S. Pat. Nos. 4,974,699, issued to Boring, 4,726,446, issued to Perbix, and 4,469,194, issued to McBride, all teach attachments to the upper end of a ladder, intended for resting, not against a roof edge, gutter or the like as in the case of the present invention, but against a Vertical wall. They are therefore not adapted to the purpose of allowing the user to step from the ladder on to the roof of the walled structure. The devices taught by Boring, Perbix and McBride would be difficult to align with a roof edge or gutter from a position at the bottom of the ladder, because of their short length. That of Boring, being of circular cross section, and that of McBride, being of narrow rectangular section would be prone to slip off a roof edge or gutter during use, probably causing damage thereto., That according to Perbix, while being short enough to cause difficulty in aligning it with the roof edge or gutter, would prevent the ladder side members of an extension ladder from sliding within one another when the ladder is shortened, in contrast to the present invention.